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  • I'm following Qt Tutorials and got a simple question

    - by nzer0
    If I want to create my own class MyWidget which inherits from QWidget Tutorial tells me to write constructor like this... MyWidget::MyWidget(QWidget *parent) : QWidget(parent){....} I'm wondering what is the role of : QWidget(parent) Does it mean explicit call for QWidget's constructor?

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  • Question about a C macro expansion

    - by holydiver
    I generally have ignored using macros while writing in C but I think I know fundamentals about them. While i was reading the source code of list in linux kernel, i saw something like that: #define LIST_HEAD_INIT(name) { &(name), &(name) } #define LIST_HEAD(name) \ struct list_head name = LIST_HEAD_INIT(name) (You can access the remaining part of the code from here.) I didn't understand the function of ampersands(I don't think they are the address of operands here) in LIST_HEAD_INIT and so the use of LIST_HEAD_INIT in the code. I'd appreciate if someone can enlighten me.

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  • Php security question

    - by Camran
    I have a linux server, and I am about to upload a classifieds website to it. The website is php based. That means php code adds/removes classifieds, with the help of the users offcourse. The php-code then adds/removes a classified to a database index called Solr (like MySql). Problem is that anybody can currently access the database, but I only want the website to access the database (solr). Solr is on port 8983 as standard btw. My Q is, if I add a rule in my firewall (iptables), to only allow connections coming from the servers IP to the Solr port nr, would this solve my issue? Thanks

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  • Question on Books

    - by rockbala
    I am a learning SQL, HTML now. I would like to learn the following two more... Java, XML. I want to understand these two from testing and Web Services point of view. Is there a better order to learn the next two Java, XML or XML, Java?

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  • iPhone "multi-threading" question

    - by MrDatabase
    I have a simple iPhone game consisting of two "threads": the main game loop where all updating and rendering happen 30 times per second (NSTimer)... and the "thread" that calls the accelerometer delegate 100 times per second. I have a variable "xPosition" that's updated in the accelerometer delegate function and used in the game loop. Is there a possibility of the two "threads" trying to use xPosition at the same time (hence causing a crash or some other problem). If so how can I fix this w/ minimal impact to the game's performance? I've been using this set-up for many months of development and incremental testing and I've never run into any problems. Cheers!

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  • Simple PHP query question: LIKE

    - by pg
    When I replace $ordering = "apples, bananas, cranberries, grapes"; with $ordering = "apples, bananas, grapes"; I no longer want cranberries to be returned by my query, which I've written out like this: $query = "SELECT * from dbname where FruitName LIKE '$ordering'"; Of Course this doesn't work, because I used LIKE wrong. I've read through various manuals that describe how to use LIKE and it doesn't quite make sense to me. If I change the end of the db to "LIKE "apples"" that works for limiting it to just apples. Do I have to explode the ordering on the ", " or is there a way to do this in the query?

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  • A question about making a C# class persistant during a file load

    - by Adam
    Apologies for the indescriptive title, however it's the best I could think of for the moment. Basically, I've written a singleton class that loads files into a database. These files are typically large, and take hours to process. What I am looking for is to make a method where I can have this class running, and be able to call methods from within it, even if it's calling class is shut down. The singleton class is simple. It starts a thread that loads the file into the database, while having methods to report on the current status. In a nutshell it's al little like this: public sealed class BulkFileLoader { static BulkFileLoader instance = null; int currentCount = 0; BulkFileLoader() public static BulkFileLoader Instance { // Instanciate the instance class if necessary, and return it } public void Go() { // kick of 'ProcessFile' thread } public void GetCurrentCount() { return currentCount; } private void ProcessFile() { while (more rows in the import file) { // insert the row into the database currentCount++; } } } The idea is that you can get an instance of BulkFileLoader to execute, which will process a file to load, while at any time you can get realtime updates on the number of rows its done so far using the GetCurrentCount() method. This works fine, except the calling class needs to stay open the whole time for the processing to continue. As soon as I stop the calling class, the BulkFileLoader instance is removed, and it stops processing the file. What I am after is a solution where it will continue to run independently, regardless of what happens to the calling class. I then tried another approach. I created a simple console application that kicks off the BulkFileLoader, and then wrapped it around as a process. This fixes one problem, since now when I kick off the process, the file will continue to load even if I close the class that called the process. However, now the problem I have is that cannot get updates on the current count, since if I try and get the instance of BulkFileLoader (which, as mentioned before is a singleton), it creates a new instance, rather than returning the instance that is currently in the executing process. It would appear that singletons don't extend into the scope of other processes running on the machine. In the end, I want to be able to kick off the BulkFileLoader, and at any time be able to find out how many rows it's processed. However, that is even if I close the application I used to start it. Can anyone see a solution to my problem?

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  • Question on Virtual Methods

    - by bobber205
    IF both methods are declared as virtual, shouldn't both instances of Method1() that are called be the derived class's Method1()? I am seeing BASE then DERIVED called each time. I am doing some review for an interview and I want to make sure I have this straight. xD class BaseClass { public: virtual void Method1() { cout << "Method 1 BASE" << endl; } }; class DerClass: public BaseClass { public: virtual void Method1() { cout << "Method 1 DERVIED" << endl; } }; DerClass myClass; ((BaseClass)myClass).Method1(); myClass.Method1(); Method 1 BASE Method 1 DERVIED

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  • A stupid question in if block

    - by priyanka.sarkar_2
    I have a very stupid issue if (updateYN.ToUpper() != Constants.NO || updateYN.ToUpper() != Constants.N) { // execute code for any other updateYN } I am trying to perform a filteration that if the value of updateYN is not NO(Constants.NO) or N(Constants.N), then execute the statement. But the problem is that , irresptive of the values , the if block is executing. What wrong is there Thanks

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  • C pointer question, dereferencing crash

    - by skynorth
    Why do this work? int *var; while(scanf("%d", &var) && *var != 0) printf("%d \n", var); While this does not? int *var; while(scanf("%d", &var) && var != 0) printf("%d \n", var); Doesn't * (dereference operator) give you the value pointed by the pointer? So why does *var != 0 crash the program, while var != 0 does not?

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  • Objective C memory management question with NSArray

    - by Robert
    I am loading an array with floats like this: NSArray *arr= [NSArray arrayWithObjects: [NSNumber numberWithFloat:1.9], [NSNumber numberWithFloat:1.7], [NSNumber numberWithFloat:1.6], [NSNumber numberWithFloat:1.9],nil]; Now I know this is the correct way of doing it, however I am confused by the retail counts. Each Object is created by the [NSNumber numberWithFloat:] method. This gives the object a retain count of 1 dosnt it? - otherwise the object would be reclaimed The arrayWithObjects: method sends a retain message to each object. This means each object has a retain cont of 2. When the array is de-allocated each object is released leaving them with a retain count of 1. What have I missed?

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  • Eclipse Type Hierarchy Question

    - by Tom Tresansky
    In Eclipse, the Java Method Override Indicator is the little upwards arrow next to a method in the Type Hierarchy view. A solid arrow means a method overrides an existing method lower in the hierarchy. What does the hollow arrow mean? Do annotations effect either arrow?

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  • Javascript Pointers question with Dates

    - by Mega Matt
    I noticed this situation in my code (unfortunately), and was able to duplicate it in my own JS file. So I have this code: var date1 = new Date(); // today var date2 = date1; date2 = date2.setDate(date2.getDate() + 1); // what is date1? After this code executes, date1 is today's date + 1! This harkens back to my undergrad days when I learned about pointers, and I guess I'm a little rusty. Is that what's happening here? Obviously I've moved the assignment away from date1, and am only modifying date2, but date1 is being changed. Why is this the case? Incidentally, after this code executes date2 is a long number like 1272123603911. I assume this is the number of seconds in the date, but shouldn't date2 still be a Date object? setDate() should return a Date object... Thanks for the help.

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  • Interview question: C program to sort a binary array in O(n)

    - by Zacky112
    I've comeup with the following program to do it, but it does not seem to work and goes into infinite loop. Its working is similar to quicksort. int main() { int arr[] = {1,1,0,1,0,0,0,1,0,1,0,1,0,1,0,1,0,1}; int N = 18; int *front, *last; front = arr; last = arr + N; while(front <= last) { while( (front < last) && (*front == 0) ) front++; while( (front < last) && (*last == 1) ) last--; if( front < last) { int temp = *front; *front = *last; *last = temp; front ++; last--; } } for(int i=0;i<N;i++) printf("%d ",arr[i]); return 0; }

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  • jquery - DOM traversal question

    - by David
    Hi, Basically what I have here is a button that adds a new list item to an unordered list. Within this list item is a dropdown box (.formSelector) that when changed triggers an ajax call to get the values for another dropdown box (.fieldSelector) in the same list item. The problem is on this line: $(this).closest(".fieldSelector").append( If I change it to $(".fieldSelector").append( the second box updates correctly. The problem with this is that when I have multiple list items it updates every dropdown box on the page with the class fieldSelector, which is undesirable. How can I traverse the DOM to just pick the fieldSelector in the current list item? Any help is greatly appreciated. Complete code: $("button", "#newReportElement").click(function() { $("#reportElements").append("<li class=\"ui-state-default\"> <span class=\"test ui-icon ui-icon-arrowthick-2-n-s \"></span><span class=\"ui-icon ui-icon-trash deleteRange \"></span> <select name=\"form[]\" class=\"formSelector\"><? foreach ($forms->result() as $row) { echo "<option value='$row->formId'>$row->name</option>"; }?></select><select class=\"fieldSelector\" name=\"field[]\"></select></li>"); $(".deleteRange").button(); $('.formSelector').change(function() { var id = $(this).val(); var url = "<? echo site_url("report/formfields");?>" + "/" + id; var atext = "ids:"; $.getJSON(url, function(data){ $.each(data.items, function(i,item){ $(this).closest(".fieldSelector").append( $('<option></option>').val(item.formId).html(item.formLabel) ); }); }); }); return false; });

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  • javascript basics question

    - by refge
    i have this small javascript code which i need some help with. function doFocus(text) { if (text.value == "Enter Name") { text.value = "Student Name -" } } All i need here is when someone clicks on my textbox, the text "Student Name -" should change its color, and should text-align=left. so text.color and text.align or the appropriate sytax.

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  • Simple stream read/write question in java

    - by Marius
    Hi, I'm trying to upload a file via URLConnection, but i need to read/write it as a binary file without any encoding changes. So i've tried to read byte[] array from FileInputStream, but now i have an issue. The PrintWriter object i use for outputing to the server does not allow me to do writer.write(content) (where content is of type byte[]). How can i fix this? Or is there another way to quickly copy binary data from a FileInputStream to a PrintWriter? Thank you

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  • Python Class Variables Question

    - by zyq524
    I have some doubt about python's class variables. As my understanding, if I define a class variable, which is declared outside the init() function, this variable will create only once as a static variable in C++. This seems right for some python types, for instance, dict and list type, but for those base type, e.g. int,float, is not the same. For example: class A: dict1={} list1=list() int1=3 def add_stuff(self, k, v): self.dict1[k]=v self.list1.append(k) self.int1=k def print_stuff(self): print self.dict1,self.list1,self.int1 a1 = A() a1.add_stuff(1, 2) a1.print_stuff() a2=A() a2.print_stuff() The output is: {1: 2} [1] 1 {1: 2} [1] 3 I understand the results of dict1 and list1, but why does int1 behavior different?

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  • Python for loop question

    - by Joe Dunk
    I was wondering how to achieve the following in python: for( int i = 0; cond...; i++) if cond... i++; //to skip an run-through I tried this with no luck. for i in range(whatever): if cond... : i += 1

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  • question on find value in array

    - by davit-datuashvili
    i have seen a few days ago such problem there is given two array find elements which are common of these array one of the solution was sort big array and then use binary search algorithm and also there is another algorithm- brute-force algorithm for (int i=0;i<array1.length;i++){ for (int j=0;j<array2.length;j++){ if (array1[i]==array2[j]){ //code here } } it's complexity is O(array1.length*array2.length); and i am interested the first method's complexity is also same yes? because we should sort array first and then use search method binary search algorithm's complexity is log_2(n) so it means that total time will be array.length*log_2(n) and about sort? please explain me which is better

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